With the development of antenna technologies, a large amount of antennas may be placed at a transmitting side. Efficiency and reliability of system transmission may be improved by joint transmission of multiple antennas. 3-dimensional (3D) beam-forming in a multiple input multiple output (MIMO) system is one of such technologies, which increases antenna gain, decreases inter-antenna co-channel interference, and is a hot candidate technology of a long-term evolution (LTE) system Release 13.
FIG. 1 is a schematic diagram of a network architecture of the 3-dimensional beam-forming technology. As shown in FIG. 1, in order to support a relatively good beam-forming technology, a base station end needs to acquire beam direction information of a user equipment (UE) end. A conventional method relies on an implementation technology of the base station end. For example, by using reciprocity of uplink and downlink channels, a direction of downlink beam-forming is estimated via the uplink channels. In a 3D MIMO system, each antenna port may include multiple antenna elements, and a width of a beam becomes narrow obviously. Thus, antenna gain becomes larger, inter-beam interference becomes more complex, and influence of beam selection and coordination on the performance of the system becomes larger.
It should be noted that the above description of the background is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.